# Iron has a melting point of 1538 °C, whereas oxygen has a boiling point of −183 °C. Both substances consist of particles, but their physical properties are very different. Explain, in terms of particles, why iron is a solid at room temperature whilst oxygen is a gas at room temperature.

> Pearson Edexcel International GCSE Chemistry (4CH1) — 1.1 States of matter · Explain · 4 marks

> Iron has a melting point of 1538 °C. Oxygen has a boiling point of −183 °C. Room temperature is approximately 25 °C.

## Mark scheme (4 marks)

1. Iron particles are held together by strong (metallic/electrostatic) forces of attraction
2. A large amount of energy is needed to overcome the forces in iron, so it remains solid at 25 °C (well below 1538 °C)
3. Oxygen molecules have weak intermolecular forces between them
4. Only a small amount of energy is needed to overcome the intermolecular forces in oxygen, so oxygen is a gas at 25 °C (well above −183 °C)

## Key terms

- [gas](https://www.gradenine.co.uk/glossary/gas)
- [solid](https://www.gradenine.co.uk/glossary/solid)
- [particles](https://www.gradenine.co.uk/glossary/particles)
- [melting point](https://www.gradenine.co.uk/glossary/melting-point)
- [boiling point](https://www.gradenine.co.uk/glossary/boiling-point)

## Related

- [Revision notes for Pearson Edexcel International GCSE Chemistry (4CH1)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/iron-has-a-melting-point-of-bf0f8166) · Published by Druglandscape Ltd.